Semiconductors are widely used to fabricate integrated circuits for electronic devices such as computers and televisions. These integrated circuits typically combine many transistors on a single crystal silicon chip to perform complex functions and store data. Semiconductor and electronics manufacturers, as well as end users, desire integrated circuits which can accomplish more in less time in a smaller package while consuming less power. One way of achieving such disparate desires can be to decrease the dielectric constant of the insulator, or dielectric, which separates conductors.
Probably the most common semiconductor dielectric is silicon dioxide, which has a dielectric constant (“k-value”) of about 3.9. In contrast, air has a dielectric constant of about 1.0. Consequently, many strategies to lower the dielectric constant of dielectrics involve replacing portions of solid dielectrics with air by increasing the porosity of these materials. In order to obtain low dielectric constants in materials that are already highly porous, the number of hydroxyl groups in the structure may desirably be minimized, especially at pore surfaces. Without dehydroxylation in some form, the dielectric constant of porous silica or organosilicate films can exceed that of substantially non-porous, dense silica, i.e., hydroxylated porous silica or organosilicate films may have a dielectric constant as high as about 4.
Prior art attempts at dehydroxylation of porous silica and organosilicate films have focused on heating the films via application of thermal heat, and/or treatment of the films via one or more silyating agents. Porous silica and organosilicate materials need to be processed at very high temperatures, e.g., over 800° C. in order to be highly dehydroxylated. Many semiconductor devices, however, cannot tolerate such high heat, and dehydroxylation may thus typically be carried out at temperatures of only from about 350 to 400° C. As such, only partial dehydroxylation may be seen, and the desired dielectric constant may not be achieved. Also, many known silyating agents may exhibit limited effectiveness, or may require application in large amounts to provide maximum efficacy. Finally, many known silyating agents can be highly flammable, or even explosive, thereby requiring the use of special equipment and/or handling procedures in order to use these agents safely.
It would thus be desirable to provide a method for reducing the dielectric constant of porous silica materials that could yet be readily, easily and economically integrated into a manufacturing process for a silica containing semiconductor device. It would also be desirable to provide compositions comprising one or more silyating agents that could be less flammable than the silyating agent(s) alone, while yet retaining their effectiveness, or even a method of using known silyating agents in a fashion that enhances their effectiveness.